Dual phase mouth wash compositions are known in the art. U.S. Pat. No. 4,525,432 provides for mouth wash compositions which comprise an oily and aqueous phase, which are mixed just prior to their use. Preferably, such compositions are essentially detergent-free. As stated therein, the use of detergents in the oral cavity has an adverse effect, such as gum recession, circulatory impairment, hyperdydration of exposed tissue, edema, as well as allergic reactions. U.S. Pat. No. 6,465,521 provides for a dual phase mouth rinse which comprises an aqueous phase, a water immiscible oily phase, and a cationic surfactant from about 0.003 to about 2.0% weight to enable the formation of a temporary oil-in-water emulsion, wherein the emulsion breaks down and separates within a period of about 10 seconds to thirty minutes after the formation of the emulsion. However, it has been found that such compositions do not completely separate into oil and aqueous phases, and a thin emulsion may be observed between the oily and aqueous phases which persists for longer than 30 minutes. The thin emulsion may adhere to the container, which contains the composition, and remains adhered to the container even after subsequent mixing of the composition. The presence of the emulsion may be unattractive to users of the composition, as the presence of such emulsion might connote the presence of contaminants, successive “rings” of the emulsion remain adhered to the container after each use, or that the composition does not completely separate into aqueous and oily phases.
One of the benefits of a dual phase mouth wash composition is that the hydrophobic phase generally resides above the hydrophilic phase as the hydrophilic phase is generally more dense than the hydrophobic phase. Such a configuration is beneficial to the stability of actives that reside in the hydrophilic phase, as actives are commonly degraded by oxidation, e.g., when exposed to air. The separation of the hydrophobic phase on top of the hydrophilic phase essentially prevents or inhibits the oxidation of such actives. Thus, in compositions where the hydrophobic and hydrophilic phases do not completely separate, e.g., emulsion remains after allowing the composition to remain at rest, the actives in the hydrophilic phase are subject to degradation by oxidation. Thus, there is a need to develop oral care compositions comprising a hydrophilic and hydrophobic phase which separates into two distinct phases, and does not contain a microemulsion created by mixing the phases together.